It is standard, for example, in the dental field to have to make a very accurate model of a patient's bite, for instance for the production of prosthetics, bridges, and the like. Thus a mold spoon filled with impression material is used to create a negative from which a positive of plaster or hard impression material is then made. In turn this positive is fitted in a mold that is filled around the positive with silicone or a similar elastic material that is then allowed to cure. Once cured, the positive master is separated from the material which therefore forms an accurate negative mold.
In the simplest procedure as described in German patent 3,541,719 filed 26 Nov. 1985 by H. Diehl the positive is provided with an imbedded magnet or magnetically attractable body and is held thereby to the floor of a mold-making mold. This mold floor is subsequently used as part of the final mold for forming the model.
German Utility Model 7,800,950 of A. Schmidseder describes a system where special supports are provided to hold the master between a pair of mold halves. After curing of an impression mass in the mold halves about the master, the mass can be separated at the level of the supports to split it into two halves and free the master. German patent application P 24 40 261.7 of G. Haker describes a retainer ring for holding together two mold halves of the type described in the Schmidseder system.
These systems do not make it simple or in some cases even possible to reproduce holding formations or so-called splits that are provided on the bottom of the master to hold it in an articulator or like holder. These formations, which can be specially formed bumps or recesses that engage with complementary formations of the articulator, are essential to subsequent working on the models.